Surface Properties and Bond Strength Measurements of N-vinylcaprolactam (NVC)-containing Glass-ionomers

Objectives: This study investigates the effect of NVC-containing terpolymers on the surface properties (e.g. contact angle and work of adhesion) and bond strength to dentin of GIC. In addition, the effect on NVC containing terpolymers as a conditioner on dentin was evaluated. Methods: The terpolymer of acrylic acid (AA)–itaconic acid (IA)–N-vinylcaprolactam (NVC) with 8:1:1 (AA:IA:NVC) molar ratio was synthesized by free radical polymerization and characterized using 1H-NMR and FTIR. The synthesized terpolymer was used in glass ionomer cement formulations (Fuji IX GP). Specimens were mixed and fabricated at room temperature. Surface properties (wettability) of modified cements were studied by contact angle measurements as a function of time. Work of adhesion values of different surfaces was also determined. The effect of NVC modified polyacid, on bond strength of glass-ionomer cement to dentin was investigated. The mean data obtained from contact angle and bonding strength measurements were subjected to one way- analysis of variance (ANOVA) at α = 0.05. Results: NVC modified glass ionomer cements showed significantly lower contact angles (θ=46o) and higher work of adhesion (WA=60.33 erg/cm2) in comparison to commercially available Fuji IX GP (θ=57o and WA=53.01 erg/cm2), respectively. The wettability of dentin surfaces conditioned with NVC containing terpolymer was higher (θ=22o, WA= 73.77 erg/cm2) than dentin conditioned with GC dentin conditioner (θ=29o, WA=70.52 erg/cm2). The experimental cement also showed higher but not statistically significant values for shear bond strength to dentin (8.5 ± 1.2 MPa), when compared to control group (8.3 ± 0.8 MPa). Conclusions: It was concluded that NVC-containing terpolymers can enhance the surface properties of GICs and also increase their bond strength to the dentin. Furthermore, NVC-containing polyelectrolytes are better dentin conditioners than a commercially available dentin conditioner (GC dentin conditioner).